I don’t think Apple has ever promoted Helvetica Neue as being more legible than, say, Lucida Grande. Apple has moved to Helvetica because it’s more attractive, and, with modern display resolutions (especially retina displays), Helvetica is legible enough. One may fairly argue that legibility should always trump aesthetics — but one could argue thus for all font choices, not just UI fonts.

The same was true of Mac OS X 10.0’s pervasive system-wide anti-aliasing. It was less legible but more aesthetically pleasing. In the long run, as displays got better and better, people stopped complaining about it.

If I’m complaining less, it’s only because I’ve lost hope that Apple is ever going to make legibility a priority. Retina displays are not yet widely available on Macs. Even where they are available, Apple has foundwaystoreduce legibility.

Seriously, a company that is actively working to make UI elements less discoverable and intuitive does not care about legibility. As far as Helvetica being more attractive…meh. Maybe hipsters like it, but I think it’s a boring, cramped, overly-light font, and it sucks for reading on-screen.

Good point and I've no idea what Apple does to fonts these days. I pretty much got used to it over the years and was happy with Mountain Lion, but Mavericks took a step backwards. Now after using Yosemite, I long to be back on anything prior to 10.10 - I almost can't use Yosemite. Not sure if it's the skinny fonts, or KDE-like elements all over the UI which makes reduces legibility , but the nail in the coffin are the transparent menus. Can turn off transparency but legibility is still an issue and with the dishwater grey colour all over the UI, it's no longer pleasurable to use OS X.

Wish Apple would just stick with the 10.7-10.9's menu colour/transparency/fonts.